I don't think liberal zoning is the problem. I've seen my city go through massive changes in the last 30 years, top of the list being a radical increase, a liberalization, of zoning. They are allowing more and bigger developments. Multi-story and multi-unit developments are everywhere, but that isn't making housing any more affordable. A piece of land with a liberal zoning is worth more. It is a target for redevelopm…
I highly doubt this is going on over any long period of time. If there's a bubble like this, it'll pop.
Why do you think these new apartments are luxury apartments? It's because living in your city is a luxury that people with enough money are paying for. If they didn't exist, people would be paying even more for living spaces that do exist. So, build new apartments and prices go up. But don't build new apartments, and prices go up more.
The most reliable way to get affordable housing (besides a lottery or waiting list, which doesn't solve the problem) is to have built new housing 30 years ago.